You know, I was in the same exact position when I took my first weld test. No work history as a welder at all. You're just going to have to wow them and make them understand that, yes, you do have experience, but it's just not on paper. If they only test you on one material and one process, request more. Force them to see you're good. If you don't actually have the goods for something like that, atleast you stand a chance to get in as a welder's helper/assistant, and learn from there. Every shop is different. I'd call them to see what they want you to test on, so you can be prepared. That first test I was talking about was on 1/2" to 3/4" MS plate w/ dual shield. All I brought were work gloves (thinking I was going to be using short arc) and ended up with a blister the size of a baseball on the back of my left hand. I kept welding, as I truley needed the job. I tried to hide the blister, but the foreman saw it through my glove. (!) (that was the first time I ever ran dual shield, and I was testing uphill........looked horrible) I convinced him to let me run some TIG and some short arc and got the job, and when I showed up, he personally taught me how to run dual shield.
The point to my ramblings is that you never know, so just try your best and be persistant.